Previously, for example, by having a light detecting element such as a photodiode or the like in a pixel, a display device with an optical sensor, which is capable of detecting brightness of outside light and capturing an image of an object near the display, has been proposed. It is contemplated that such a display device with the optical sensor is used as a bi-directional communication display device, or as a display device with a touch panel function.
In a conventional display device with an optical sensor, when known constituting elements, such as a signal line, a scan line, a TFT (Thin Film Transistor), a pixel electrode and the like, are formed by a semiconductor process on an active matrix substrate, at the same time, a photodiode and the like are formed on the active matrix substrate (for example, see Patent Document 1).
There is a temperature dependence in a light detecting element, such as a photodiode and the like. In order to compensate for changes in characteristics of the element due to a change in an ambient temperature, a configuration in which a light detecting element for reference is provided in addition to the light detecting element for detecting brightness has been known (for example, see Patent Document 2). The configuration, as disclosed in Patent Document 2, has a light blocking area covered by a light blocking film in a part of a pixel region, and compensates a light signal read out from the light detecting element formed in a display area not covered by the light blocking film, with an output of the light detecting element in the light blocking area. By this, a sensor output, which is compensated for a change in a dark current accompanying the ambient temperature change and which therefor is not subject to the temperature change, can be obtained.